This invention relates to elastomers. In one aspect, this invention relates to ethylene-propylene (EP) and ethylene-propylene-diene monomer (EPDM) elastomers while in another aspect, this invention relates to a process for their manufacture. In yet another aspect, this invention relates to elastomers made by a process in which the catalyst is a metallocene complex, more particularly to a class of Group 4 metal complexes.
Metallocene complexes and methods for their preparation are disclosed in U.S. Ser. No. 82,197 filed Jun. 24, 1993 (abandoned); U.S. Ser. No. 230,051 filed Apr. 19, 1994 (abandoned); U.S. Ser. No. 241,523 filed May 12, 1994 (now U.S. Pat. No. 5,470,993); U.S. Ser. No. 469,186 filed Jun. 6, 1995 (now U.S. Pat No. 5,624,878); U.S. Ser. No. 470,858 filed Aug. 15, 1995 (now U.S. Pat. No. 5,556,928) U.S. Ser. No. 545,403 filed Jul. 3, 1990 (pending, and of which EP-A-416,815 is an equivalent); U.S. Ser. No. 547,718 filed Jul. 3, 1990 (abandoned in favor of continuation U.S. Ser. No. 896,732 which is now U.S. Pat. No. 5,321,106, and of which EP-A-468,651 is an equivalent); U.S. Ser. No. 702,475 filed May 20, 1991 (abandoned in favor of continuation-in-part U.S. Ser. No. 967,365 which is pending, and of which EP-A-514,828 is an equivalent); U.S. Ser. No. 876,268 filed May 5, 1992 (now U.S. Pat. No. 5,721,185, and of which EP-A-520,732 is an equivalent) and U.S. Ser. No. 8,003 file Jan. 21, 1993 (now U.S. Pat. No. 5,374,696, and of which WO93/19104 is an equivalent), as well as U.S. Pat. Nos. 5,055,438, 5,057,475, 5,096,867, 5,064,802 and 5,132,380. The teachings of all of the foregoing United States patents are incorporated herein by reference.
The term xe2x80x9celastomerxe2x80x9d was first defined in 1940 to mean synthetic thermosetting high polymers having properties similar to those of vulcanized natural rubber, e.g. having the ability to be stretched to at least twice their original length and to retract very rapidly to approximately their original length when released. Representative of these xe2x80x9chigh polymersxe2x80x9d were styrene-butadiene copolymer, polychloroprene, nitrile rubber, butyl rubber and ethylene-propylene terpolymers (aka EPDM rubbers). The term xe2x80x9celastomerxe2x80x9d was later extended to include uncrosslinked thermoplastic polyolefins, i.e. TPO""s.
ASTM D 1566 defines various physical properties, and the test methods for measuring these properties, of rubbers. U.S. Pat. No. 5,001,205 (Hoel) provides an overview of the known elastomers comprising ethylene copolymerized with an xcex1-olefin. As Hoel describes, commercially viable elastomers have various minimum properties, e.g. a Mooney viscosity no less than 10, a weight average molecular weight (Mw) no less than 10,000, a glass transition temperature below xe2x88x9240 C., and a degree of crystallinity no greater than 25%. U.S. Pat. No. 5,001,205 discloses a process for polymerizing high molecular weight elastomers using liquid phase polmerization in the presence of a metallocene/alumoxane (i.e., bis(cyclopentadienyl)alumoxane) catalyst.
We have now discovered a process for the manufacture of ethylene-propylene and ethylene/xcex1-olefin/diene monomer polymers. In one embodiment, the process comprises the steps of:
A. contacting in a first reactor (1) ethylene, (2) at least one C3-C20 aliphatic xcex1-olefin, (3) optionally, at least one C4-C20 diene, (4) a catalyst, the catalyst comprising (a) a metallocene complex, and (b) at least one activator, and (5) a solvent, the first reactor operated such that a first product is produced at a solids concentration of from about 1 to about 15 weight percent, based on the weight of the reaction mass in the first reactor;
B. contacting in a second reactor (1) ethylene, (2) at least one C3-C20 aliphatic xcex1-olefin, (3) optionally, at least one C4-C20 diene, (4) a catalyst, the catalyst comprising (a) a metallocene complex, and (b) at least one activator, (5) a solvent, and (6) a product stream from the first reactor, the second reactor operated such that a second product is produced at a solids concentration of from about 2 to about 30 weight percent, based on the weight of the reaction mass in the second reactor;
C. removing a product stream from the second reactor;
D. removing solvent from the product stream of the second reactor in an anhydrous, first stage solvent recovery operation such that the solids concentration of the product stream is increased by at least about 100 percent; and
E. removing additional solvent in an anhydrous, second stage solvent recovery operation from the product of the the first stage solvent recovery operation such that the solids concentration of the product stream is in excess of 65 weight percent.
In another embodiment of this invention, the process comprises additional anhydrous solvent recovery operations in which the solids concentration of the final product is increased to greater than 99 weight percent. Preferably, the product of the first reactor has a weight average molecular weight greater than that of the product of the second reactor.
In yet another embodiment, the process comprises the steps of:
A. contacting in a first reactor (1) ethylene, (2) at least one C3-C20 aliphatic xcex1-olefin, (3) optionally, at least one C4-C20 diene, (4) a catalyst, the catalyst comprising (a) a metallocene complex, and (b) at least one activator, and (5) a solvent, the first reactor operated such that a first product is produced at a solids concentration of from about 1 to about 30 weight percent, based on the weight of the reaction mass in the first reactor;
B. contacting in a second reactor (1) ethylene, (2) at least one C3-C20 aliphatic xcex1-olefin, (3) optionally, at least one C4-C20 diene, (4) a catalyst, the catalyst comprising (a) a metallocene complex, (b) at least one activator, and (5) a solvent, the second reactor operated such that a second product is produced at a solids concentration of from about 1 to about 30 weight percent, based on the weight of the reaction mass in the second reactor;
C. recovering a product stream from each of the first and second reactors, and then blending these individual product streams into a combined product stream;
D. removing solvent from the combined product stream in an anhydrous, first stage solvent recovery operation such that the solids concentration of the combined product stream is increased by at least about 100 percent; and
E. removing additional solvent in an anhydrous, second stage solvent recovery operation from the combined product stream such that the solids concentration of the combined product stream is in excess of 65 weight percent.
In another embodiment of this invention, the process comprises additional anhydrous solvent recovery operations in which the solids concentration of the final product is increased to greater than 99 weight percent. Preferably, the product of one reactor has a weight average molecular weight greater than that of the product of the other reactor.